Electric switch mechanism



Jan. 23, 1962 J. EGGERT EFAL 3,018,340

ELECTRIC SWITCH MECHANISM Filed July 2, 1959 INVENTOR5 I 5' Law/5 Jzi'aaflzr. W lV/AL/AM S. TuFrs.

d l ow United States Patent 3,018,340 ELECTRIC SWITCH MECHANISM Lewis J. Eggert, Worthington, and William S. Tufts,

Columbus, Ohio, assignors to Ranco Incorporated, Columbus, Ohio, a corporation of Ohio Filed July 2, 1959, Ser. No. 824,518 3 Claims. (Cl. 200-38) The present invention relates to improvements in an electrical switch mechanism of the type comprising a rotatable cam having a surface on which one or more switch members ride and which surface has a step portion which drops at least one switch member relative to the other to cause a making or breaking of an electrical circuit.

The principal object of the invention is the provision of an improved electrical switching mechanism of the type mentioned in which one of the switch members comprises a resilient blade which can be adjustably positioned relative to the cam so that the angular position of the cam at which the blade drops from the step on the cam surface can be accurately established and which adjustment can be elfected by merely deflecting the blade by simple means, such as a screw.

In carrying out the aforementioned objects, the invention comprises the combination of a housing or base on which a rotatable cam is supported, the cam having a surface including a rise and a step or drop-off intermediate high and low points of the rise surface, and which cam surface is engaged by a pair of co-engageable switch members, one of which comprises a resilient blade formed with two sections disposed at less than a straight angle with one another, one section being anchored to the base and the opposite end of the other section being disposed tangentially to the cam so as to ride on the cam surface, means being provided adjacent to the anchored position of the blade for flexing the blade whereby the end edge thereof engaging the cam surface may be shifted angularly relative to the axis of the cam and thereby change the angular position of the cam at which the blade end leaves the high portion of the step. The resiliency of the blade is utilized to maintain the blade in engagement with the flexing means, which may consist of a screw threaded in an opening in a member carried on the base and abutting the spring arm. Thus, the adjustment of the blade relative to the cam can be accurately effected by exceedingly inexpensive elements.

Other objects and advantages of the invention will be apparent from the following description of a preferred form thereof, reference being had to the accompanying drawings wherein FIG. 1 is an end view of an electrical timer motor driven switching mechanism embodying the invention, a cover of the switching mechanism being removed and certain switch members being shown broken away;

FIG. 2 is a fragmentary view of the switching mechanism shown in FIG. 1, but illustrating certain switch members in different positions;

FIG. 3 is a View similar to FIG. 1, but showing certain contact members in still other positions; and

FIG. 4 is a view taken substantially along line 4-4 of FIG. 1.

In the preferred form of the invention shown, the switching mechanism is embodied in an electric motor driven timer which may be utilized to control sequential operation of an appliance, such as a clothes dryer, and is capable of controlling two electrical circuits so that after a predetermined period of operation of the timer one circuit is opened and the other is closed, and after a second predetermined period the first circuit is reclosed and the second is reopened. It is to be understood, however,

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2 that the invention could be embodied in timing mechanisins to control any other suitable circuits desired.

Referring to the drawings, the timer shown includes an open side box type housing or base 10 formed of molded insulating material, such as Bakelite, and which may be closed by a suitable cover, which has been removed from the housing. A cam 11 is rotatably supported within the housing by a shaft 12 which is driven at a suitable rate, such as one revolution per hour, by an electric constant speed synchronous motor operating through a gear reduction train, neither of which are shown inasmuch as such mechanisms are well known in the art and are not necessary to an understanding of the invention. Cam 11 includes a slightly undercut step 13, the top and bottom of which are joined by a gradually rising slope 14. Provision may be made for rotating shaft 12 manually to set the timer for operation, but for sake of simplicity in this disclosure, this well known expediency is omitted.

The switch mechanism comprises three flat, b-lade type spring'members -15, 16 and 17 which are anchored at one end to housing 10 and their opposite ends carry contacts 15a, 16a (which is a double contact as shown), and 17a, respectively, which are disposed so that contact 16a can be engaged by either of contacts 15a or 17a, and the blades are all inherently biased toward the surface of cam 11. Blades 15 and 17 are maintained separated by a spacer 18 formed of rigid insulating material and having the central portion extending through an opening through blade 16 and the opposite ends are reduced and extend through openings in blades 15 and 17, as best seen in FIG. 1. By this arrangement the two outer blades are maintained in predetermined space relationship while contact 16a carried by blade 16 may be engaged by either of contacts 15a or 17a. It will be noted that the end of blade 16 projecting beyond contact 16a overlies the end of blade 15 so that this end may ride on the high portion of the cam surface 14 after blade 15 has dropped to the low portion, as shown in FIG. 2.

It 'will be seen that when cam 11 is rotated clockwise from the position shown in FIG. 1, the high edge of step 13 will pass the right hand end edge 15b of blade 15 which will then drop to the foot of step 13 causing the end of blade 16 to drop and ride on the high portion of surface 14, which causes contacts 15a and 16a to separate and blade 17 to drop and engage contact 17a on contact 1 6a, as shown in FIG. 2. By this action, an established circuit through contact 15a and 16a is broken and a circuit may be established through contacts 16a and 17a. Upon further clockwise rotation of cam 11, the end of blade 16 drops from step 13 and re-engages contact 16a with contact 15a, and due to spacer 18, contact 17a is separated from contact 16a, as may be seen in FIG. 3. Thus, the original circuits may be reestablished after a given period which is determined by the angular rotation of cam 11 required to traverse the high edge of step 13 from the end edge of blade 15 to the end edge of blade 16. This angle is illustrated at a in FIG. 1, by lines representing planes intersecting the axis of the cam and passing through the end edges of blades 15 and 16 which engage cam surface 14.

The present invention resides in the provision of inexpensive means for accurately adjusting angle a," thereby providing for close setting of the time interval between the switch operations described.

Blades 16 and 17 are rigidly anchored at their left hand ends to terminal members 20 and 21, respectively, which are embedded or otherwise suitably attached to the housing or base 10 and which provide means for connecting the respective contact blades in the circuits desired to be controlled.

Blade 15, on the other hand, is bent in a generally L-shape form, having a vertically extending section 15c,

as viewed in the drawings, and a section 15d projecting tangentially of the ca m. Section 15c is anchored by a rivet 15s to a bar 23 rigidly secured to housing 10, as by embedding in the material thereof. A portion of blade section 15c is offset from the anchored portion and biased to engage the right hand of a screw 24 threaded in an opening formed through bar 23, the left hand end of which screw projects through an opening a through a side wall of housing 10 so as to be accessible for adjustment by a screwdriver. It will be apparent that by adjusting screw 24 in the opening in bar 23 section 150 of blade follows the end of the screw, flexing toward and from cam 11 and which, due to the angular form of the blade, causes section 15d to move longitudinally and shift the end edge 15b tangentially relative to the cam surface to thereby increase or decrease angle a, and adjustably varying the time interval at which blades 15 and 16 drop from step 13. This adjustment is illustrated by the full and broken lines of FIG. 1 showing the portion of blade 15 riding on the cam surface in two different positions. Angle a illustrates one angular adjustment providing one period of time between switch operations and angle b illustrates a shorter period effected by threading screw 24 inwardly. It will be apparent that exceedingly accurate adjustment of the position of blade 15 relative to the cam can be easily accomplished by screw 24, and the arrangement as shown is quite simple and can be incorporated in switching mech anism of the type disclosed with but little expense.

It will be understood that blade 16 could be adjusted in a manner similar to that described with reference to the adjustment of blade 15 and such modification would be clearly within the scope of the invention.

While we have described but one form of the invention, other forms, modifications and adaptations might be employed, all falling within the scope of the claims which follow. i

We claim:

1. In an electric switching mechanism comprising a base, a cam rotatably supported on said base and having a switch actuating surface including a rise portion and a step, a pair of contact arms each arranged to have one end ride on said surface and to sequentially move between the extremities of said step as said cam is rotated to move said step beyond the end edges of said contact arms engaging said cam, one of said arms comprising a blade type spring member having one section at an angle of substantially less than 180 with the other section thereof, means to anchor said one section to said base whereby said other section extends tangentially of said cam and bears on said surface of said cam so that said one section may flex and shift said other section longitudinally, and means adjacent to said anchored end of said blade for adjustably flexing said section to shift the end of said one other section tangentially relative to said cam surface.

2. In an electric switching mechanism comprising a base, a cam rotatably supported on said base and having a switch actuating surface including a rise portion and a step, a pair of contact arms each arranged to have one end ride on said surface and to sequentially move between the extremities of said step as said cam is rotated to move said step beyond the end edges of said contact arms engaging said cam, one of said arms comprising a resilient blade having one section at an angle of substantially less than with the other section thereof, means to anchor said one section to said base whereby the other section extends tangentially of said cam and bears on said surface of said cam so that said one section may flex and shift said other section longitudinally, means providing a threaded opening adjacent to the anchored portion of said one contact arm, and a screw threaded in said opening and having one end engaging said one section, said one section being spring biased against said end of said screw.

3. In an electric switching mechanism comprising a base, a cam rotatably supported on said base and having a switch actuating surface including a rise portion and an abrupt step, a pair of contact arms each arranged to have one end ride on said surface and to sequentially snap move between the extremities of said step as said cam is rotated to move said step beyond the end edges of said contact arms engaging said cam, one of said arms comprising a resilient blade having one section at an angle of substantially less than 180 with the other section thereof, means to anchor said one section to said base whereby said other section extends tangentially of said cam and bears on said surface of said cam so that said one section may flex and shift said other section longitudinally, said means comprising a bar bracket member attached to said base, means attaching said one section of said one contact arm to said bracket, a screw threaded through an opening in said bar and engaging said one section and adapted to flex said one section and thereby move said other section of said one arm tangentially relative to said cam.

References Cited in the file of this patent UNITED STATES PATENTS 2,504,002 Crum Apr. 11, 1950 2,562,481 Swayze July 31, 1951 2,690,526 Morrison Sept. 28, 1954 2,736,173 Duncan Feb. 28, 1956 

